While it’s early days–and we don’t have a time machine to see what the future will hold–there’s some very promising data from Israel about the efficacy of a third mRNA vaccination dose (aka The Booster) in preventing confirmed infection. Not just severe cases or death, but infection, which would be critical in stemming transmission. From the preprint (boldface mine):
The rate of confirmed infection was lower in the booster group than in the nonbooster group by a similar factor across the age groups: 12.4 (95% confidence interval [CI], 11.9 to 12.9) for people 60+ years of age, 12.2 (95% CI, 11.4 to 13.1) for people aged 50-59, 9.7 (95% CI, 9.2 to 10.4) for people aged 40-49, 8.8 (95% CI, 8.2 to 9.5) for people aged 30-39, and 17.6 (95% CI, 15.6 to 19.9) for people aged 16-29. Interestingly we find a higher increase in protection at the youngest age group (16-29). The absolute between-group difference in the rate of confirmed infection was 61.8 infections per 100,000 person-days for people 60+ years of age, 75.2 for people aged 50-59, 89.4 for people aged 40-49, 97.7 for people aged 30-39, and 80.2 for people aged 16-29. In the secondary analysis, we saw a similar pattern, namely, the rate of confirmed infection after at least 12 days from receipt of the vaccine was substantially lower than the rate 3 to 7 days after booster receipt: 7.4 (95% CI, 7.0 to 7.8) for people 60+ years of age, 7.3 (95% CI, 6.7 to 7.9) for people aged 50-59, 5.4 (95% CI, 5.0 to 5.8) for people aged 40-49, 4.8 (95% CI, 4.4 to 5.2) for people aged 30-39, and 11.2 (95% CI, 9.9 to 12.8) for people aged 16-29.
Here it is in figure form:
Note this fold increase in protection against confirmed infection represents the first boldface part; earlier work by the same group in people aged 60 and older showed there’s a roughly two-fold effect of behavioral differences between the two groups.
I’ll get to the caveats in a moment, but this reduction in confirmed infections likely would be large enough in all groups to get R less than one–that is, transmission would be low enough to stop wide-scale spread (when enough people are vaccinated). Encouragingly, the protective effect is strongest in the youngest cohort. That matters because kids and grandkids murder their parents and grandparents: to protect middle-aged and older people, we need to prevent infection in younger people (of course, younger people avoiding long COVID is a benefit too).
All that said, there are caveats. First, we don’t know how long this effect will persist or how much it could decline, though in most cohorts, even a substantial fold-drop likely would still be effective enough. Second, the effect of a third dose obviously doesn’t matter when too many people don’t have their first and second doses. Third, it’s possible, though I think highly unlikely, that a third dose merely reduces symptoms but not spread (i.e., most of us would be asymptomatic spreaders).
But assuming these caveats don’t turn out to be correct and there is long-term protection against infection that confers lower transmission with a third dose, what might that mean for policy?
In America, 2021, Year of Our Gritty, the reality (still) is we’re unlikely to adopt non-vaccine interventions widely enough because we have been unable and unwilling to do so to date. For example, improving ventilation in buildings (including schools) would be great and should be done, but we can’t even deliver rent assistance which just consists of mailing checks, so how are we going to repair so many buildings? Widespread testing? The U.S.’s regulatory apparatus is too hidebound, and the cost of at-home testing is still too high, especially for those who need to test the most. Let’s not even start with the multiple failures surrounding masks and mask wearing. As we were reminded during the Democratic primaries, the U.S. isn’t Denmark–and that is obvious at this point.
What magical thing will happen that suddenly lifts the scales from people’s eyes and leads to a widespread adoption of all of these other public health measures–which are expensive and require ongoing effort? After eighteen months, it’s clear we lack both the structures of governance and civic virtue to respond in a widespread, sustained manner. We must accept America as it is, not as it ought to be or could be.
All we have left in the public policy arsenal is getting enough people vaccinated–which is to say, we mandate vaccination much more than we have to date–and hoping that vaccination is effective. The other approaches have failed in the U.S. They could work, but we simply won’t use them enough because America is too dysfunctional. So we’re left with vaccination, which is a dreadful hope, but it’s all we have. Otherwise, it’s just a kinder, gentler Great Barrington Declaration all the way down.
Right now, we have to wait and see.